BMW iX Big Brake Kit Upgrade / TTSPORT Classic 8657S
A BMW iX built for spirited driving and the occasional track day doesn't get much help from its stock brakes once things get hot — pedal feel goes soft and stopping power tapers off just when you need it most. This install case from BAC (彼斯博克) swaps the factory front setup for a TTSPORT Classic Series 8657S big brake kit, aimed squarely at giving the iX a firmer pedal and more consistent stopping power under sustained hard driving.
The car runs 22-inch wheels, and the front axle was upgraded to TTSPORT's TT8657S six-piston caliper paired with a 405mm carbon high-temperature-treated rotor — a straightforward front-axle upgrade rather than a full four-corner conversion.
Vehicle & Kit Specs
| Item | Specification |
|---|---|
| Vehicle | BMW iX, 22-inch wheels |
| Front caliper | TTSPORT TT8657S six-piston caliper (Classic Series) |
| Front rotor | TTSPORT 405mm carbon high-temperature-treated rotor |
| Bracket | Custom vehicle-specific caliper bracket |
| Pads / lines | TTSPORT high-performance street pads, stainless steel brake lines |
| Hardware | Brake fluid, mounting bolts, and fixing hardware |
Below is TTSPORT's official spec sheet for the 8657S caliper used in this build.
| Brake Caliper | |
|---|---|
| Series | Classic Series |
| Model / Application | 8657S |
| Axle Position | Front |
| Piston Count | 6-piston |
| Piston Type | Two-piece heat-insulated pistons with dust boots |
| Piston Diameter | 30 mm × 2 / 34 mm × 2 / 38 mm × 2 |
| Caliper Dimensions | L 350 mm × W 165 mm × H 92.64 mm |
| Total Piston Area | 55.0 cm² per caliper, all pistons combined |
| Manufacturing Process | Two-piece forged aluminum body |
| Net Weight | 4.05 kg per caliper, without pads |
| Surface Finish | High-temperature gloss coating |
| Recommended Wheel Size | 18 in or larger |
| Recommended Rotor Size | Ø355–405 mm × 32–34 mm |
| Fitment & Installation | |
| Minimum Spoke Clearance (mm) | 107 |
| Caliper Mounting Type | Radial mount with vehicle-specific caliper brackets |
| Brake Line Fitting Type | Vehicle-specific fittings; caliper-side and chassis-side fittings vary by application |
The 8657S is TTSPORT's revised take on the earlier TT8657, with changes to piston sizing, caliper venting, and overall caliper dimensions. It carries over the two-piece forged aluminum body that keeps the caliper stiff while limiting unsprung mass — weight that, when reduced, helps the suspension do its job more effectively.
Why It Works
- Two-piece forged construction keeps the caliper body rigid under load, so pedal input goes into clamping force instead of caliper flex — the core fix for a soft, mushy stock pedal.
- The two-piece heat-insulated pistons resist heat transfer into the brake fluid, helping guard against the fade that shows up on long descents or repeated hard stops.
- Progressive piston sizing (30/34/38mm) applies pad pressure gradually across the six pistons, which is what gives the pedal a linear, predictable feel rather than an on/off bite.
- The 405mm rotor adds mass and surface area over the stock disc, giving the system more thermal capacity to absorb and shed heat during sustained braking.
- With a 107mm minimum spoke clearance requirement, the 8657S was engineered to fit behind the iX's 22-inch wheels without spacers.
Installation Gallery
What does the TTSPORT 8657S kit include for the BMW iX?
Does the 8657S kit clear the stock 22-inch wheels on this iX?
What changed in the 8657S caliper compared to the earlier TT8657?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.